Position indicator switch with yieldingly spaced cylindrical contacts having wiping action



June 24, 1969 D. STEWART 3,452,168

POSITION INDICATOR SWITCH WITH YIELDINGLY SPACED CYLINDRICAL CONTACTSHAVING WIPING ACTION Filed DeC. 27, 1966 ATfOR/YE Y 3,452,168 CED D.STEWART June 24, 1969 R SWITCH WITH YIELDINGLY SPA ONTACTS HAVING WIPINGACTION m0 ML IA c M D m u HG S Sheet 2 01'2 Filed Dec. 2'7, 1966ATTORNEY United States Patent US. Cl. 200-6152 4 Claims ABSTRACT OF THEDISCLOSURE This invention relates to improvements in circuit breakersand more specifically to tilt-actuated circuit breakers, the contacts ofwhich are caused to either make or break upon tilting of the circuitbreaker carrier member, with respect to a reference plane, of thecarrier member. Such a carrier member may include the landing gear truckof modern aircraft.

This application relates to a copending patent application entitled,Improvements in Position Indicator Switches, by David Stewart, filedNov. 23, 1966, and having U.S. Ser. No. 596,684.

Failure of many prior art circuit breaker switches to function properlyoccurs by short circuits arising from the accumulation of water within asupposedly air-tight or sealed switch case. Any air leak passageway intotypical sealed switch cases acts as a Water trap. Sources of such watertraps are imperfect soldering techniques and the unpredictable life ofthe switch actuator shaft seal.

Later switch designs have abandoned the sealed or air tight approach andhave introduced a vented case concept. This, too, has provedinefiicient: the vent typically does not clean itself of dust particlesand is open to water ingestion when the switch case is subject to waterenvironments; insulation material used in many of the vented switchcases is Water absorbent. Such insulation having absorbed water reduceselectrical insulation, promotes tracking and causes switch contact armsto hang up.

It is an object of the teachings of this invention to provide a vehicletilt-actuated switch having no lifelimiting factors built into it. Theswitch is designed to last indefinitely, requiring only occasionalcleaning and inspection.

A further object of the teachings of this invention is to provide acircuit breaker switch capable of handling contaminating environments towhich it is subjected. Contaminants which ordinarily cause short circuitproblems include water, cleaning solutions, and oil. A feature of theteachings of this invention provides that should such contaminants assand or dust particles acquire entrance into the swicth case, no failureof the switch to operate will occur.

A further object of the teachings of this invention is to provide meansfor eliminating, as far as posible, all bearings and pivots so thatworking parts will be as few and simple as posisble.

Briefly, the teachings of this invention are directed to an improvementin vehicle position actuator level switches. The switch is essentiallycomprised of a plurality of movable electrical contact means such a twoelectrical contact arms, each carrying contact elements collectivelycomprising the plurality of contact means. The contact means aredisposed to be actuated and be given movement relative to one another byan actuator means. More particularly, the contacts are supported uponthe contact arms to rotate toward and away from each other about asupporting shaft. A ventilation assembly is provided in combination withcontainer means which enclose the circuit 3,452,168 Patented June 24,1969 breaker or level switch. The vent assembly is provided for keepingthe switch clean by allowing the passage of air therethrough and isconstructed in the form of a labyrinth to prevent dust or foreignparticles from reaching the switch contacts. Such a switch findsparticular utility on the truck assembly of aircraft landing gear. Thetruck beam must bear a definite angle relationship to the landing gearstrut or aircraft structure. Any tilting of the truck assembly willactivate the switch of this invention to provide the pilot with a signalindication. The signal indication serves to advise the pilot when thetruck assembly leveling mechanism has failed to work. In this case,danger exists that the aircraft wheels will catch on aircraft structureduring landing gear retraction or lowering. Total failure of the landinggear to lock down could then occur and result in serious accidents.

This invention will appear more clearly from the following detaileddescription when taken in connection with the accompanying drawings,showing by way of example the preferred embodiment of the invention.

In the drawings:

FIGURE 1 is a cutaway perspective of a vehicle position or tilt-actuatedlevel switch according to the teachings of this invention;

FIGURE 2 is an assembly detail of the actuator switch according to theteachings of this invention;

FIGURE 3 is a section view of the vehicle tilt-actuated level switchaccording to the teachings of this invention;

FIGURE 4 shows the movable electrical contact means wherein the contactsare separated from one another;

FIGURE 5 is a perspective section view of the vent assembly according tothe teachings of this invention;

FIGURE 6A shows the movable electrical contact means having contact withone another;

FIGURE 6B shows the moveable electrical contact means just prior tocontact with one another.

Referring to the drawings, FIGURE 1 shows a perspective view of avehicle tilt-actuated level switch 10, according to the teachings ofthis invention. Metal casing means 12 and removable casing lid 12Aenclose the switch mechanism described below in detail. Lid 12A isflanged over casing 12 to improve sealing capability. Electrical outlet16 is attached to the casing means 12 by means (not shown) such assoldering. Electrical leads 15 interconnect the outlet 16 with movablecontact arms or means 18. The electrical leads 15 are supported withincasing 12 by bracket 13. Integrally connected to the contact means 18are contact elements 20 and 21.

Continuing with reference to FIGURES l and 2, the electrical contactarms or means 18 are shown disposed for attachment to a pair of Delrynarms 25 by screws 19. The contact arms 18 are restrained in the positionas shown in FIGURE 1 by means of spring 26 extensions 24 biasing againstpins 47 which are fixedly attached to the Delryn arms 25. Spring 26 isso designed that under nontilt conditions the extension 24 biasesagainst the pins 47 so as to bring the contact arms 18, suported on theDelryn arms 25, into the position as shown in FIGURE 1, i.e., withphysical contact existing between the semicylindrical contacts 20 andthe cylindrical contact 21. By using two spring contact arms 18 insteadof two pivoted levers, pivot friction or possible seizure at pivotpoints has been eliminated.

Continuing with reference to FIGURE 2, a rotatable shaft 32 is disposedwithin casing 12 and supported by a bushing 37, fixedly attached tocasing 12, and a support bearing 36 integrally part of removable casinglid 12A. The rotatable shaft 32 is disposed for actuation by actuatormeans 31 which is fastened to shaft 32, once shaft 32 has been placedconcentric within bushing 37, by a cotter pin 27 through a cotter pinhole 28 in shaft 32. The Delryn arms 25 with their associated contactarms 18 are disposed axially about shaft 32 and positioned againstsupport bearing or bushing 37 by a striker means 33 having a bushing 38asociated therewith. The striker 33 is fixedly attached to shaft 32 by acotter pin 29 driven through an opening 30 in the bushing 38 whichpasses into an opening 30 in shaft 32. Thus, as actuator means 31,driven by a linkage (not shown) sensitive to tilting of switch whilesupported upon a vehicle structure, rotates shaft 32, striker 33 iscaused to rotate therewith. The spring 26 is fiitted over bushing 38 ofstriker 33 and held thereon by bushing 34 which fits concentricallywithin spring 26. Bearing 36 is integrally cast to removable casing lid12A which is tightened into position by bolts 45 shown in FIGURE 1.

Briefly in operation, separation of the contacts 20 and 21 occurs asfollows. Upon vehicle tilting, actuator means 31 causes rotation ofshaft 32 which drives striker 33 to bear against one of the pins 47, asseen in FIGURE 4, thus rotating one of the Delryn arms 25 about shaft32. The other Delryn arm 25 is restrained from similar rotation by afixed stop 49 which is fixedly attached to casing 12. Continued rotationof shaft 32 further loads the spring 26 until separation of contacts 20and 21 is complete. As the vehicle (not shown), supporting switch 10,

is returned to non-tilting position, shaft 32 is returned to itsoriginal position by actuator 31. Spring 26, free of influence ofstriker 33, returns the Delryn arms 25 to the position shown in FIGURE3, i.e., with physical contact existing between contacts 20 and 21.

The switch 10 is therefore essentially comprised of: actuator means 31responsive to change of vehicle position, and a plurality of movableelectrical contacts, e.g.,

contacts 20 and 21, disposed to move relative to one another in apivoting manner, supported by contact arms 18, about shaft 32, inresponse to the actuator means 31. The relative movement of the contacts20 and 21 is such that when the vehicle tilts, i.e., shifts positionrelative to a reference plane, the contacts 20 and 21 move in a firstdirection relative to one another; when the vehicle is restored to itsnon-tilting position, the contacts 20 and 21 move in a second directionrelative to one another and oppositely to said first direction. Whethermovement of contacts 20 and 21 in a first direction results in making orbreaking of physical contact between contacts 20 and 21 depends, ofcourse, upon the initial mounting of switch 10 upon the supportingvehicle. As shown above in the preferred embodiments, switch 10 ismounted upon a supporting vehicle (not shown) such that contacts 20 and21 are mated together, as seen in FIGURES 1 and 3, when the supportingvehicle is in its non-tilting position. Upon vehicle tilting, therefore,movement of contacts 20 and 21 in a first direction relative to oneanother will result in physical separation of contacts 20 and '21 to thecondition as seen in FIGURE 4. Continuing, as the support vehicle isrestored to its non-tilting position, movement of contacts 20 and 21 ina second direction relative to one another will result in physicalcontact or mating of contacts 20 and 21 again as seen in FIGURES 1 and3.

Continuing with reference to FIGURES 3 and 4, contact 21 is cylindrical.Contacts 20 are semicylindrical, and otherwise are similar to contact21.

With reference to FIGURES 6A and 63, lower contact 20 and upper contact20 have been given the reference letters A and B, respectively. The endportion 17a, of one of the contact arms '18 to which lower contact A isafiixed, abuts against a mechanical stop 17b. End portion 17a and stop17b serve as a second set of contacts. The contacts 20 (i.e., contacts Aand B) are sprung toward each other by their respective contact arms 18;their minimum separation is fixed by adjustable stop 22 having anadjustment screw 23. It is assumed that synchronous contact betweencontact 21 and both contacts A and B is virtually impossible and thatsimultaneous contact by the entire length of either of the cylindricalcontacts A and B with contact 21 is also impossible. It follows that asthe switch 10 makes or breaks, one end of one contact 20 (i.e., either Aor B) will 'function. For illustration, assume that one end of uppercontact B is the first and the last contact to function with contact 21.The make-break sequence will then be as follows: during the breakingcycle, the tip 17a of the lower contact A separates from the mechanicalstop 17b against which 17a abuts as seen in FIGURE 6A. Continuing toFIGURE 6B, as upper contact B slides past contact 21, lower contact Awill do so as well. After upper contact B has separated from contact 21,lower contact A separates and a spark is formed (assuming electricalcurrent flows in leads 15 from a circuit and power source not shown).The point at which the spark is formed is not the normal conductingsurface. As the contacts 20 and 21 make contact again, i.e., moving in asecond direction relative to one another, the upper contact B willstrike contact 21 first. It will do so at the point where contact wasbroken and where the contacts 20 and 21 are most liable to becontaminated. As upper contact B slides over contact 21, the spring arm18 for upper contact B will deflect torsionally until contact along thelength of cylindrical contact B and 21 is established. This length isnot contaminated by the inductive spark which initially formed. As uppercontact B continues to make contact with contact 21, it is raised upwardby the cam action of the curvature of contact 21. This relieves the loadon adjustable stop 22, and permits lower contact A to rise with itssupporting arm 18 to make contact with 21. As relative movementcontinues, contacts 20 and 21 slide past each other with a wipingaction. The line of contact on both contacts 20 and 21 continuallychanges. If it is desired to increase contact pressure, the tip 17a oflower contact A can be adjusted downward, causing it to ride along thetop of the left Delryn arm 25 as shown in FIGURE 6A.

With reference to FIGURE 5, a switch 10 venting assembly or means 42 isshown attached to casing 12 by convenient means such as bolts 44. Thevent assembly 42 comprises a metal baffie plate 46 and block of inertmaterial 50 attached by bolts 44 to casing 12. A vent hole 48 passesthrough the baffle plate 46 and the casing 12. The piece of inertmaterial 50, such as plastic or Teflon, is aligned above the vent hole48 in baffle plate 46 and held down with the bafile plate 46 to casing12 by the bolts 44. Passageways 52 through the inert material 50 areprovided allowing free air circulation through the vent hole 48 whilepreventing most solids such as dust particles and sand particles fromentering the casing 12. For a dust particle to enter into the interiorof casing 12, it would have to achieve four right-angle bends throughthe labyrinth passages 52 in the inert material 50. Since a dust or sandparticle has mass and velocity, it is diificult to see why it shouldmake even one bend through the labyrinth passages 52. Should it enterthrough the vent hole 48, it will encounter a fly-paper type of trap(not shown) within casing 12. The fly-paper trap consists of paintingthe in side of the casing 12 with a proper paint. The type of paint tobe used will have the property of sticking to particles even when it isdry. This same paint is used as a gasket material for sealing the lid12A (seen in FIGURE 1, attached by bolts 45 to casing 12). The paintdries enough to make a seal yet remains soft enough that the lid can beremoved when desired. The bolts 45 are sup ported by sleeves 45A whichare attached, as by welding, to casing 12. The bolts 45 pass throughcasing 12, within sleeves 45A, to fasten casing 12 and the switch 10 toa vehicle support structure in a given reference plane position, e.g.,horizontal or vertical or some number of degrees from horizontal.

Thus, the labyrinth of means 42 provides for water or dust to easilyleave the casing 12 but essentially prevents contaminants from enteringthe casing 12. The connector 16 is vented into the switch 10 so that nopressure difference exists between its internal air cavity and ambient.

Thus, the connector 16 will remain dry for the same reason as the switchwill remain dry.

With reference to FIGURES 3 through and including 6B, the preferredembodiment of switch 11) can be described with detail in operation- Whenthe vehicle (not shown) to which switch 10 is attached shifts positionrelative to a reference plane, actuator means 31 wil be driven to rotateclockwise or counterclockwise, depending upon the relative positionshift of the support vehicle with respect to the reference plane. Shaft32 will then rotate, with actuator means 31, within bushing 37 andbearing 36. Spring 26, not being fixedly attached to shaft 32,nevertheless tends to rotate with shaft 32 as striker 33, rotating withshaft 32, comes to drive against a pin 47 which serves to load spring26. The spring 26 is prevented from rotating, however, by fixed stop 49,fixedly attached to casing 12, aaginst which a Delryn arm 25 biases asit tends to rotate under the influence of spring extension 24 bearingagainst pin 47. Striker 33, rotating with shaft 32, continues to rotatethe Delryn arm 25, attached to the pin 47 against which striker 33bears, until the contacts 20, 21, 17a and 17b have moved in a firstdirection relative to one another and switch 10 appears as shown inFIGURE 4. This is the extreme position, however, and as is shown in FIG-URE 6B, a signal can be established (by means of circuitry not shown) ofpending dangerous shift of vehicle position relative to the referenceplane at the moment tip 17a in FIGURE 6B breaks contact with itsmechanical stop 17b on contact arm 18 so that vehicle levelingadjustment may be made before contacts 20 and 21 separate and theposition as shown in FIGURE 4 is reached.

While in the foregoing there has been shown and described the preferredembodiment of this invention, it is to be understood that minor changesin the details of construction, combination and arrangement of parts maybe resorted to wtihout departing from the spirit and scope of theinvention as claimed. Referring to FIGURE 4, for example, one might wishto mount switch 10, as shown, during non-tilting conditions. Then, asthe vehicle (not shown) to which switch 10 is attached tilts (i.e.,shifts position relative to a reference plane) actuator means 31 willcause striker 33 to unload spring 26. In this manner a signal will beestablished of pending dangerous vehicle tilt conditions when contacts17a, 17b, 20 and 21 move in a first direction relative to one anotherwhich is opposite the first direction of movement described in the abovepreferred embodiment. In other words, the contacts 17a, 17b, 20 and 21move so as to make contact and vehicle leveling adjustment is madebefore contacts 20 and 21 move together.

I claim:

1. A vehicle position actuated switch comprising:

(a) actuator means responsive to changes of vehicle position between atilt and a non-tilt condition;

(b) a first moveable electrical contact having a substantiallycylindrical contact surface;

(c) a pair of second moveable electrical contacts each having opposedsubstantially cylindrical contact surfaces yieldingly spaced apart andadapted to receive said first electrical contact therebetween; and

(d) linkage means connected between said actuator means and said firstand second electrical contacts for moving said first and secondelectrical contacts relative to each other in response to said actuatormeans between a closed position, wherein said first electrical contactis interposingly engaged between and in substantially line contact witheach of said pair of second electrical contacts, and an open position,wherein said first electrical contact is disengaged from said secondpair of electrical contacts.

2. The vehicle position actuated switch as claimed in claim 1 whereinsaid linkage means comprises:

(a) spring means for normally biasing said first and second electricalcontacts in one position; and

(b) striker means connected to said actuator means for moving said firstand second electrical contacts against the bias of said spring means tothe other position.

3. A vehicle position actuated switch comprising: (a) actuator meansresponsive to change of vehicle position between a tilt and a non-tiltcondition; (b) a pair of moveable contact arms made of electricalinsulating material;

(0) a first electrical contact carried by one of said contact arms, saidcontact having a substantially cylindrical contact surface;

(d) a pair of second electrical contacts yieldingly carried by the otherof said contact arms in spaced apart relationship, each of said secondelectrical contacts having opposed substantially cylindrical contactsurfaces adapted to receive said first electrical contact therebetween;

(e) spring means normally biasing said pair of contact arms to a closedposition wherein said first electrical contact is interposed between andengaged in substantially line contact with each of said pair of secondelectrical contacts; and

(f) striker means operatively associated with said actuator means, saidstriker means engaging at least one of said pair of contact arms toposition said contact arms in an open position against the bias of saidspring means wherein said first electrical contact is disengaged fromsaid second pair of electrical contacts.

4. A position actuated electrical switch comprising:

(a) rotatable shaft means for rotation by an actuator;

(b) a pair of contact arms each mounted rotatably about said shaft meansand made of electrical insulating material;

(c) a first electrical contact carried by one of said contact arms, saidcontact having a substantially cylindrical contact surface;

(d) a pair of second electrical contacts yieldingly carried by the otherof said contact arms in spaced apart relationship, each of said secondelectrical contacts having opposed substantially cylindrical contactsurfaces adapted to receive said first electrical contact therebetween;

(e) spring means normally biasing said pair of contact arms to a closedposition wherein said first electrical contact is interposed between andengaged in substantially line contact with each of said pair of secondelectrical contacts; and

(f) striker means attached to said shaft means for rotation therewith,said striker means engaging said pair of contact arms to rotate saidcontact arms to an open position against the bias of said spring meanswherein said first electrical contact is disengaged from said secondpair of electrical contacts.

References Cited UNITED STATES PATENTS 2,708,226 5/1955 Dixon ZOO-61.522,735,964 2/1956 Grieve et al. 317 X 2,948,785 8/ 1960 Thomas. 3,161,73712/1964 Hall ZOO-153.1 X

FOREIGN PATENTS 222,711 8/ 1962 Austria.

ROBERT K. SCHAEFER, Primary Examiner. R. A. VANDERHYE, AssistantExaminer.

US. Cl. X.R.

